Fix a typo in the CleanCouchPoller code

It can cause unexpected errors, when an error occurs
add support to stageout from HLT Cloud at CERN

The VMs on the HLT Cloud at CERN don't have access to the eos environment.
Change the stageout plugin to only use generic xrootd commands.

Patch was developed by Stephen Gowdy, I did test it in a replay though.
prevent task archiver crashing when central couch server is down
Fix how we delete documents in couchdb

A weird hitch in couch's delete semantics is that if you don't use the
DELETE verb (i.e. you commit with _bulk_docs and set _deleted=true), it
stores the whole data in the delete tombstone. See:

https://issues.apache.org/jira/browse/COUCHDB-1141

Since (AFAIK), we don't ever use _deleted_revs=true to look at things,
it means that we have tons of old data sitting around in couch that's
basically invisible. This patch strips the document before comitting it
so the only thing lefts are _id, _rev and _deleted
Merge pull request #4401 from hufnagel/cernhltstageout

add support to stageout from HLT Cloud at CERN
Merge pull request #4393 from dballesteros7/Fix-ErrorMessage-CleanCouchPoller

Fix a typo in the CleanCouchPoller code
Merge pull request #4396 from PerilousApricot/bugfix/update-couchdb-delete

Bugfix/update couchdb delete
Merge pull request #4397 from ticoann/prevent_taskarchiver_crash

prevent task archiver crashing when central couch server is down
Fixing delete stuff
Merge pull request #4404 from PerilousApricot/bugfix/update-couchdb-delete

Fixing delete stuff